Middle distillate fuel composition



MIDDLE DISTILLATE FUEL COMPOSITION Darrell W. Brownawell, Scotch Plains, and William C.

Hollyday, Jr., Plainfield, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Dec. 17, 1963, Ser. No. 331,113

10 Claims. (Cl. 44--62) This invention concerns an improved middle distillate fuel and more particularly relates to a middle distill-ate fuel containing a combination of additives that improves the flow and filterability of the fuel at low temperatures.

U. S. Patent 3,048,479 describes a petroleum distillate fuel containing a pour depressant comprising an ethylenevinyl acetate copolymer. The preferred copolymer contains from 60 to 99 wt. percent ethylene and from 40 to about 1 wt. percent vinyl acetate. The molecular weight of the copolymers should be in the range of from about 1,000 to 3,000, preferably in the range from about 1,500 to 2,200.

Employed in the middle distillate fuel in a concentration of from 0.001 to 0.5 wt. percent and preferably from about 0.005 to 0.1 wt. percent, these copolymers lower the pour point of middle distillate fuels to permit their being pumped through pipes at very low temperatures, for example, 40 F. The development of this pour depressant was recognized as being important in that prior to this development there existed serious problems in distributing heating oils, diesel fuels and jet fuels at cold temperatures. Also, the low temperature properties of petroleum distillate fuels boiling in the range of from about 250 to 750 F. have attracted increasing attention in recent years because the growth of market of such fuels in subarctic areas and because of the development of turbo-jet aircraft capable of operating at altitudes where temperatures of -50 F. or lower may be encountered.

Although the ethylene-vinyl acetate copolymer improves the flow characteristics of middle distillate fuels at low temperatures, there still exists a filterability problem. Many systems, for example, diesel engines, contain fine filter elements such as paper-element filters. These filter elements are usually placed so that they are cold at startup and are later warmed if the engine is run for a suflicient time. It has been found that many middle distillate fuels, even those containing the ethylene-vinyl acetate copolymer, deposit a nonaporous wax cake on such a filter, thus clogging the filter and stopping flow of the fuel before the engine runs for a sufiicient time to Warm the filter and thus melt the wax.

It is, therefore, an object of this invention to provide. a middle distillate fuel composition that has satisfactory fl'ow characteristics and enhanced filterability at low temperatures. v

The object of the invention is attained by employing, in combination with the ethylene-vinyl acetate copolymer, a polymer of a lauryl acrylic ester having a molecular weight of from 760 to 10,000. These acrylic esters include the polylaurylmethacrylate and polylaurylacrylate.

It is known that the ethylene-vinyl acetate copolymer cocrystallizes with the wax in the fuel oil and also adsorbs onto the surface of the formed wax crystals. Adsorption United States Patent 3,275,427 Patented Sept. 27, 1966 is the mechanism of pour depressants. Adsorption and cocrystallization of the ethylene-vinyl acetate copolymer with the wax alters the agglomeration habit of the wax to lower the pour point but does not necessarily promote the formation of aporous wax cake.

It has now been discovered that polylauryl methacrylate and polylauryl acrylate alter the agglomerate structure of the wax so as to promote the formation of a filter cake having greater porousness, thus enhancing the filterability of the fuel. Thus, by replacing a portion of the ethylenevinyl acetate copolymer with a polymer of a lau ryl-acrylic ester, one obtains a fuel that has satisfactory filterability without sacrificing the pour depressant efficacy of the ethylene-vinyl acetate copolymer.

The additive combination of this invention is useful in middle distillate fuels boiling from, 300 'to 750 F. and preferably from 400 to 675 F. Such fuels include aviation turbo-jet fuels, kerosenes, heating oils and the like. The combination is particularly useful in diesel fuels since the operation of diesel engines in cold climates requires a fuel having good filterability characteristics.

The additive combination of this invention may be employed in conjunction with a variety of other additives commonly used in fuels, such as rust-inhibitors, antiemulsifying agents, corrosion-inhibitors, anti-oxidants, dispersants, dyes, dye-stabilizers, haze-inhibitors, antistatic additives and the like. It will frequently be found convenient to prepare additive concentrates for use in the various types of fuels and add all of the additives simultaneously.

The acrylic esters of this invention should be employed in middle distillate fuel in a concentration of from 0.001% to 1.0%, preferably from 0.005% to 0.10%. The acrylic ester and the ethylene-Vinyl acetate copolymer may be easily blended (heating to a temperature of to F. will facilitate this blending) so that the additive combination can be added as a blend rather than as individual additives to the middle distillate fuels. In this event, the

acrylic ester should constitute from 10 to 90 wt. percent and preferably 25 to 75 wt. percent of the additive blend. In some instances it will be desirable to dissolve this additive blend in kerosene, to obtain a concentrate containing from 10 to 75 Wt. percent, preferably about 50 wt. percent of the additive blend.

Standard pour depressant tests were performed using.

an ethylene-vinyl acetate copolymer consisting of 75 wt. percent ethylene and 25 wt. percent vinyl acetate. Pour depressant tests were performed using the ethylene-vinylacetate copolymer alone at various concentrations and in combinations with polylaurylacrylate and polylauryl methacrylate at various concentrations and ratios of copolymer to acrylic polymer. The results appear in Tables I, II and III.

Filterability tests were performed using the abovedescribed ethylene-vinyl acetate copolymer and the acrylic polymers. This test is used to predict the behavior of diesel fuels in the filter elements, at the time of engine start-up'in cold weather. The 500 milliliter test samples were cooled to the test temperature (0 F. and 20 F.). Each sample Was then transferred quickly to :a precooled filtration apparatus wherein the sample was filtered through Whatman No. l filter paper at a vacuum of from 3 3 23 to 25 inches of mercury. The filtration was continued until filtration stopped or until air passed through the wax filter cake, releasing the vacuum. The results of these tests are given in terms of the filtration rate and the percentage of the liquid flowing before vacuum drop-01f in Tables I, II and III.

TABLE I.FILTERABILITY IMPROVEMENT OF DIESEL FUEL A Pour Filter Percent Additive 4 Point, Rate; Filtered 4 F. ml./min.

(A) Filter Test at F.:

None 0 5. 4 69 -1o 29. 3 s7 -10 a2. 4 93 0 2. 0 17 -10 1s. 3 86 -20 26.8 86 0 340. 0 as 0 304. 0 7s 0 144. o 92 0 101. 0 s1 37. 4 92 42. s 92 --10 4a. 7 9s 0I05o% PLMA .III 5 92 1 For complete description of Fuel A, see Table IV.

1 P20 is a copolymer of about 75 wt. percent ethylene and 25 wt. percent vinyl acetate. PLMA is lauryl methacrylatc polymer.

3 Filter test: 500 ml. tuel filtered through 12.5 cm. Whatman No. 1 filter paper.

4 Based on total liquid phase present (excluding solid wax phase).

TABLE II.-FILTERABILITQ%[I1\11ROVE1VIENT OF HEATING 1 For complete description of Fuel B, seeTable IV.

1 P-20 is a copolymer of about 75 wt. percent ethylene and 25 wt. percent vinyl acetate. PLA is lauryl acrylate polymer. PLMA is lauryl methacrylate polymer.

3 Filter test: 500 ml. fuel filtered through 12.5 cm. circle of Whatman No. 1 filter paper, at 20 F.

4 Based on total liquid phase present (excluding solid wax phase).

TABLE III.FILTERABILITY IMPROVEMENT OF HEATING OIL C 1 1 For complete description of Fuel C, see Table IV.. V

1 P-20 is a copolymer of about 75 wt. percent ethylene and 25 wt. percent vinyl acetate. PLA is lauryl acrylate polymer. PLMA is lauryl methacrylate polymer.

3 Filter test: 500 m1. fuel filtered through 12.5 cm. circle of Whatman No. 1 filter paper, at -20 F.

4 Based on total liquid phase present (excluding sohd wax phase).

' TAB LE IV Fuel Code Designation A B 0 Crude Source; Middle Venezuela Venezuela, v East Gulf Coast Type Straight Catalyt- Straight Run ically Run and Cracked Cracked Distillation Points, F.:

Initial 384 408 340 5% Over. 446 474 403 50% 0ver 532 556 497 Over.... 615 642 618 inal 625 660 636. Cloud Point F--- 0 +8 +26 +4 Pour Point. +20 5 Aniline Point, F 152 109 132 Density, gJml 25 0-- 0. 840 0.911 0. 854 API Gravity 35. 5 22. 5 33.0 Viscosity, cs./ F 3. 21 3. 62 2. 44.,

The data in Tables I, It and n1 indicate that the ethylene-vinyl acetate copolymer is an effective pour depressant in three ditferent middle distillate fuels. Polylauryl acrylate and polylauryl methacrylate used alone are not efiective pour depressants in many base stocks. However,

the data in the above tables indicate that the acrylic polymers can be used to replace up to one-half of the ethylene vinyl acetate copolymer without sacrificing pourydepression to obtain satisfactory filtera'bility. In Table I, one observes that the .fuel containing only the ethylene-vinyl acetate copolymer (0.025 wt. percent) required 13.4 minutes for 87% of the fuelto pass through the filter at 0 F. In

contrast, without loss of pour depression efiicacy, the fuel containing the combination e f-polylauryl. methacrylate' (0.006 wt. percent) and ethylene-vinyl acetate copolymer (0.019 wt. percent) required only 5.1 minutes at F. for 93% of the fuel to pass through the filter. Similar results were also observed atminus 20, F. -20, F.)

and were observed with a number of combinations of ethylene-vinyl acetate copolymers with acrylic polymers as illustrated in Tables I, II and III.

What is claimed is:

1. A middle distillate fuel boiling in the range of from a 300 to 750 F. containing a minor amount sufficient to to enhance the filterability of said fuel of a polymer of a lauryl acrylic acid ester having a molecular weight of from 760 to 10,000.

2. A fuel according to claim 1 wherein the copolymer is a copolymer of ethylene and vinyl acetate and wherein said polylaurylacrylic acid is polylaurylmethacrylate.

3. A middle distillate fuel boiling in the range of from 300 to 750 F. containing from about 0.001 to 0.5 wt. percent of an ethylene-vinyl acetate copolymer having a molecular weight of from about 1000 to 3000 wherein said copolymer contains about 15 to 25% of vinyl acetate; and from 0.001 to 1.0 wt. percent of a polylaurylmethacrylate having a molecular weight of from 760 to 10,000.

4. An additive blend useful in middle distillate fuels to give satisfactory pour depression and to enhance filterability at cold temperatures, said blend comprising from 90 to Wt. percent of an oil-soluble copolymer of ethylene and a vinyl fatty acid ester, said copolymer being further characterized by containing from about to 30 wt. percent of said vinyl fatty acid ester; and from 10 to 90 wt. percent of a polymer of a lauryl-acrylic acid ester having a molecular weight of from 760 to 10,000.

5. A blend according to claim 4 wherein acrylic acid ester is polylaurylmethacrylate.

6. A blend according to claim 4 wherein said acrylic acid ester is polylaurylacrylate.

7. A blend according to claim 4 wherein said lauryl- 6 acrylic acid ester constitutes from 25 to wt. percent of said blend.

8. An additive blend useful in middle distillate fuels to give satisfactory pour depression and to enhance filterability at cold temperatures, said blend comprising from to 10 wt. percent of an oil-soluble copolymer of ethylene .and a vinyl fatty acid ester having from about 3 to 5 carbon atoms in the ester, said copolymer having a molecular weight in the range of from about 1000 to 3000, said copolymer being further characterized by containing from about 15 to 30 wt. percent of said vinyl fatty acid ester; and from 10 to 90 wt. percent of a polymer of a lauryl-acrylic acid ester having a molecular weight of from about 760 to 10,000.

9. A blend according to claim 8 wherein said copolymer is 'a copolymer of ethylene and vinyl acetate and wherein said lauryl-acrylic acid ester is polylauryl methacrylate.

10. A blend according to claim 8 wherein said laurylacrylic acid ester is polylauryl acrylate.

References Cited by the Examiner UNITED STATES PATENTS 2,403,267 7/ 1946 Davis 44-62X 3,048,479 8/1962 Ilnyckyj et a1. 44-62 DANIEL E. WYMAN, Primary Examiner;

Y. M. HARRIS, Assistant Examiner. 

1. A MIDDLE DISTILLATE FUEL BOILING IN THE RANGE OF FROM 300 TO 750*F. CONTAINING A MINOR AMOUNT SUFFICIENT TO LOWER THE POUR POINT OF SAID FUEL OF A COPOLYMER OF ETHYLENE AND A VINYL FATTY ACID ESTER HAVING FROM ABOUT 3 TO 5 CARBON ATOMS IN THE ESTER, SAID COPOLYMER BEING FURTHER CHARACTERIZED BY CONTAINING FROM 15 TO 25% OF SAID VINYL FATTY ACID ESTER; AND A MINOR AMOUNT SUFFICIENT TO ENHANCE THE FILTERABILITY OF SAID FUEL OF A POLYMER OF A LAURYL ACRYLIC ACID ESTER HAVING A MOLECULAR WEIGHT OF FROM 760 TO 10,000. 